Method of preparing a gas interchangeable with coke oven gas, carbureted gas, or mixtures thereof



Oct. 19, 1954 c. H. RlEsz ET AL 2,692,193

METHOD OF' FREPARING A GAS INTERCHANGEABLE WITH COKE 4OVEN GAS, CARBURETED GAS OR MIXTURES THEREOF y Pl'fe C. .Zz/Zazie @M mwmgg 2 Sheets-Sheet 2 C. H. RIESZ ETAL www OVEN GAS, CARBURETED GAS OR MIXTURES THEREOF 1948 oct. 19, 1954 Filed July 29,

'zn'cz'zzg Gai ydzdmzdz Patented Oct. 19, '1954 METHGD OF PREPARING A GAS INTER- CHANGEABLE WITH COKE OVEN GAS, CARBURETED GAS, 'OR MIXTURES THEREOF Charles H. Riesz and Pierre C. Lurie, Chicago, Ill., assgnors to The Institute of Gas Technology, Chicago, Ill., a. corporation of Illinois Application July 29, 1948, Serial No. 41,351

This invention relates to method and apparatus for gas manufacture particularly .adapted to meet periodic peak demands for domestic gas.

With the increasing demand for gas as a premium fuel for domestic house heating, seasonal variation in gas sendout has been growing from year to year. To meet the resulting peak demands, it is desirable to produce and feed a substitute gas into the mains, or pipelines. Where such feeding is effected in outlying areas far from the main gas generating plant, the substitute gas is fed into the pipelines counter to the normal flow from the main gas generating plant. For this purpose, a substitute gas that is completely interchangeable with the normal sendout gas must be used, since the region Where the two gases will meet Will vary with the load. More particularly, the substitute gas should have the same specific gravity and heating value as the normal sendout gas.

Such interchangeable substitute gas has been prepared by cracking propane or butane in the presence of steam in a one-stage process, using a nickel catalyst. Such concurrent catalytic cracking and blue gas reaction yield a carrier gas of low gravity (0.40 or higher) and high hydrogen content (50% to 60%). This carrier gas is characterized by a heating value of less than 325 B. t. u. Gases of higher heating value cannot be prepared from propane or butane by catalytic cracking and concurrent reaction with steam without deposition of carbon or an accumulation of naphthalene and tar in the condensing and cooling system, bringing about a pressure block necessitating plant shut-down. The

carrier gas obtained by such catalytic cracking in the presence of steam is enriched with propane or butane vapors and the specific gravity of the resulting mixture is adjusted, if necessary, with air, flue gas or the like to form a finished substitute gas having, say, a specific gravity of about 0.70 and a heating value of from 520 to 550 B. t. u. The finished substitute gas can be made completely interchangeable with normal sendout gas, such as carburetted Water gas, natural gases, coke oven gas or mixtures thereof or other city gases.

A plant for making a substitute gas by the above described process is particularly adapted for use in meeting seasonal or periodic peak de- 4 Claims. (CLS-214) mands, since the plant investment and maintenance costs are low and the plant is characterized by high capacity, exibility and reliability. It should be understood that the material costs are of secondary importance, since the total quantity of gas produced during peak loads is a relatively small percentage of the total sendout.

From a cost standpoint, one of the larger items of cost in the operation of the plant referred to hereinabove is the cost of storing butane or propane which require storage under pressure, being normally gaseous.

Attempts have been made to prepare a carrier gas by concurrent catalytic cracking and reaction with steam and/or air, using as starting materials cracked gasoline, kerosene, gas oil distillates, crude naphtha or other normally liquid hydrocarbons containing appreciable amounts of aromatic or oleiinic hydrocarbons. However, these attempts have turned out to be unsuccessful because of the occurrence of heavy carbon deposits on the catalyst or the formation of relatively large amounts of oily or tarry material fouling the condensing and cooling systems.

TJi/'e have now provided method and apparatus by which liquid hydrocarbon products containing considerable amounts of aromatic or olenic constituents may be cracked and concurrently reacted with steam, air or mixtures thereof to form a carrier gas of the type indicated, without deposition of carbon and without formation of oily or tarry material. More particularly, we pass the vapors of a normally liquid hydrocarbon or hydrocarbon mixture containing appreciable amounts of aromatics or olenes, in admixture with steam or air or mixtures thereof, through a tube maintained at from 800 to 1700 F. This tube may be empty or may contain a low activity cracking catalyst, such as alumina, silica, various clays and the like. The product issuing from this tube includes a gas fraction and a vapor fraction. The gas fraction contains a large amount of hydrogen, together with considerable amounts of carbon monoxide, carbon dioxide, illuminants, methane and ethane. The vapor fraction constitutes upwardly of 20% of the total amount of discharged material, for instance, from 40% to 60%, and can be condensed at lower temperatures to form a liquid of different boiling range than the material charged into the tube. The material discharged from the above mentioned tube is passed through a second tube maintained at from 1000 to 2000D F. and containing an active cracking catalyst such as nickel or nickel oxide. In this second tube, the gases and vapors are cracked and concurrently reacted with steam, air or mixtures thereof to yield a carrier gas comparable to the carrier gas obtained by catalytic cracking of propane and concurrent Areaction''with steam', air or mixtures thereof. In-sp'te-ofl the fact thatthe material fed into the second tube contains a major proportion of a normally liquid hydrocarbon product having a boiling point higher .than the orig.-

inal starting material, no carbonis'depositediin'.

the second tube, nor is any significant amount of oily or tarry material obtained. This absence of carbon deposits and of tar is quite surprising in View of the fact that thecriginal starting material would yield carbon and tars` if fed directly into the second tube and in further' vievv` of the fact that a major portion-of-'the material..

passing into the second tube is a normally liquid hydrocarbon mixture of at least as great'mole'cular Weight and as complex as the original starting material.

The gaseous fraction of the product discharged from the rst tubeA has a relatively high heating value due to its hydrocarbon content, for instance, about 625B. t; u. If desired, this gaseous fraction can be separated from the accompanying vapor fraction and then used to enrich the carrier gas from the second tube. In this event, the carrier gas can be produced as disclosed hereinabove, the stream from the first tube being split so that part of the stream` is conducted to the second tube and another part is conducted to a condenser forl fractionation into a gaseous an'd a liquid portion. 1f desired, this liquid portion can thenbe vaporized and incorporated4 with the stream entering the second tube.

@ther modications of the above described process are possible and Will be described below. We' note inthis connection,.that the apparatus and methods of the present. invention oier certain advantages (mentioned hereinbelow) for the gasification of hydrocarbon mixtures. devoid of olenic or aromatic constituents. It is, therefore, an important object of the present invention to provide methods for manufacturing a substitute gas completely inter,- changeable with the normal sendout gas of a gas generating plant, the starting material being a normally liquid hydrocarbon mixture that cannot be directly catalytically cracked and concurrently reacted vvith steam, air or mixtures thereof Without carbon deposition andtar formation, and the carrier gas obtained from the starting material being enriched with gases or vapors of high heating value, for instance, propane or butane vapors or gas obtained by cracking hydrocarbon oils or the like.

Another object of the present invention is to provide method for manufacturing a'carrier gas suitable for enrichment with propane or butane vapors or the like from a normally liquid hydrocarbon mixture containing appreciable amounts of olenic and aromatic constituents and not susceptible to direct catalytic cracking and concurrent reaction with steam, air or mixtures thereof Without carbon deposition and tar Vformation.

A further object of this invention is to provide method for' manufacturing a substitute gas interchangeable with normal sendout gas starting With a normally liquid hydrocarbon mixture and comprising the step of rst cracking said mixture While reacting the same with steam, air or mixtures thereof to form a p-roduct including a vapor fraction and a gas fraction of high heating value, further cracking the product of said first step While concurrently reacting the product with air, steam or mixtures thereof to form a' carrier gas: off 10W heating z value; subjecting addition'alamounts of saidlmixturetoxsaid nrst cracking step, separating the gaseous fraction ofhigh heating value obtained from said additional amount, and enriching said carrier gas with said-Lseparated gaseous fraction.

Other.'l and. further objects and features of the presentinventionivvill become apparent from the following description and appended claims taken in. conjunctionL with the appended drawings in which Figure 1"is= a'- oW-sheet illustrating one method for preparingfasubstitute gas according to the present invention.

Figure 2 is a iiovv sheet illustrating another form of the method of the invention.

Figure '3= illustrates: diagrammatica-lly-a suitableA apparatus for carrying out the processv of Figure 1..

Proceeding; accordingto themethod illustrated in yFigureY 1,. they starting hydrocarbon material I is rst vapcrizedvandA thereafter mixed; with superheated steam 2,. The resulting mixture 3 of; superheated steam and hydrocarbon vapors is pa'ssedithrough a first; reaction tube Tl. The materials passed into therst, reaction tube may be at atemperaturefof. 450 F. or, higher before reaching;y theI tube; This tube; is externally or otherwiseheated to maintain a temperature therein of fronr800 to. 1700i F., preferably 1000.o to- 1400o F. 'Ihe tube may bel empty or. may contain. a low activity cracking. catalyst, for in.- stance,.bauxite,.activated clays of the .montmorillonite: type, mixtures of alumina and silica, of magnesia and silicaor the like.. Theamount of steam admixed with the hydrocarbon material may range from.0.5. poundto l0 or 12 pounds of steam ior eachpound of hydrocarbon material.

Under. the conditions specied, a. product 4 is discharged fromA the rst. reaction tube made up of. a vapor fraction and. a gas fraction. The vapor fraction may amount to` 20% or more, for instance, from 40 to 60%. The gas, fraction may containabout 50% hydrogen,v from 5 to 15% carbonmonoxide, from 5v to 15% carbon' dioxide, from 10. to 30% illuminants, v.from 5 to 15% methane, and 2 to 10% ethane. The presence of the carbon. oxides indicates the likelihood that a blue gas reaction (water gas. reaction) takes place in the first tube.

Next, the material 4' discharged from the rst tube is passed through a second or catalyst tube T2. containing an activel cracking catalyst such as nickel ornickel oxide, nickel sulphide, nickel thiomolybdate, iron or iron oxides, molybdenum oxide or sulde, or the like. Preferably, these catalysts are distributed over suitable Supporting material. In case of nickel, for instance, the supporting material may be refractory bricks cr fragments thereof of appropriate size, other ceramic bodies, magnesite, alumina and` bauxite, activated clays, magnesia, silica, or mixtures of silica with alumina or magnesia. An excellent catalyst can be prepared by soaking porous alundum spheres of suitable diameter in a concentrated nickel nitrate solution .and heating the spheres at 1000 F., or higher, for instance 1400 F., to form nickel oxide. The nickel content of the ignited spheres should run from 3 to 10% as metallic nickel) or more.

The second catalyst tube is externally heated to maintain therein a temperature of from 1000o to 2000 F., preferably from 1300 to 1850 F.

The mixture 5 of gas and steam discharged from the second tube is passed through a condenser Ci to remove water t, leaving carrier gas l which is mixed with air, carbon dioxide or flue gas 8 and with an enriching gas or vapor 9 such as propane or butane vapor, to yield a finished substitute gas I 0.

Under the conditions indicated hereinabove the carrier gas 'i will be characterized by a heating value of from about 200 to 325 or 350 B. t. u. Typically the gas will contain about 50 to 60% hydrogen, the remainder including from 15 to 25% or more carbon monoxide and from 5 to 15% carbon dioxide together with the nitrogen content of any added air or flue gas.

. By way of a preferred modification of the above described process, air in amounts up to 100 cubic feet per pound of hydrocarbon material (or carbon dioxide or nue gas) may be mixed with product il, to form a mixture of high heating value gas, hydrocarbon vapor, steam and air or carbon dioxide or flue gas, which is then passed through the second tube T2. The added air aids in maintaining the desired temperature in the second tube and reduces the amount of steam required for preventing carbon deposition. Because of its nitrogen content, this air can be utilized in controlling the specific gravity f the nished substitute gas. l'f no nitrogen is desired in the substitute gas, the corresponding amounts of oxygen may be incorporated With the mixture passing into the second tube in place of the air.

Other modifications include the incorporation of air or carbon dioxide or flue gas with the mixture of hydrocarbon vapors and steam 3, to form a mixture of steam, hydrocarbon vapors and air or carbon dioxide or flue gas which is then passed into the first tube Ti. Likewise, the gas mixture issuing from the second tube T2 may be recycled to the first tube T I Further modications include the addition of steam to the gas and vapor mixture 4 discharged from the first 'tube TI, which mixture is then passed into the Second tube T2. In this case, part of the total amount o1" steam, for instance, from i0 to 60% may be added to the mixture passing into the first tube TI and the remainder into the mixture passing into the second tube T2. The total amount of steam may be the same as that added in the simplest method or in the preferred method disclosed hereinabove, and the gas and vapor mixture issuing from the rst tube TI may be processed further according to either of said last mentioned methods.

Figure 2 illustrates a further basic modification in which the product [i from the first tube TI may be fractionated in a condenser C2 into a gas fraction il of high heating value suitable for enriching the carrier gas, and into a liquid fraction l2. The liquid I2 is vaporized in a suitable heater HI and the vapors I3 are blended with superheated steam to form a mixture I4 which may be passed through the catalytic reactor tube T2 to produce a gas I5. The gas l5 isenriched by adding gas fraction il from the condenser C2 and the gravity adjusted by adding heavy gases 8, to produce the final product gas. The mixture Ii may also have air, carbon dioxide or flue gas added thereto and the resulting mixture thereafter passed into the secondY tube T2.

Instead of steam, air or carbon dioxide 0r iiue gas, in amounts up to cubic feet per pound of hydrocarbon may be mixed with hydrocarbon vapors I and the resulting mixture passed through the first tube TI. Steam is then generated in the first tube, by partial combustion of the hydrocarbon vapors, so that the reaction in the first tube is effected in the presence of steam.

It is believed possible that in the above described methods there is effected in the first tube a light selective thermal cracking of long chain parairins, oleflns and of aromatics coupled with a blue gas reaction. In the second tube, further cracking and additional blue gas reaction may take place. In the second tube, the cracking is effected catalytically. In both tubes the cracking is brought about in an atmosphere containing steam and hydrogen. Besides taking part in the blue gas reaction, the steam serves to equalize the temperatures in the externally heated tubes and to reduce the tendency toward carbon deposition. The air that may be present in the mixture entering one or both tubes serves not only to raise the temperature but to reduce the tendency to carbon deposition and to improve the resistance of the catalyst against sulfur. The carbon dioxide formed as a result of reaction of the hydrocarbon with Steam or with air, or deliberately added to the reaction mixture, serves as an inert diluent reducing the tendency to carbon deposition and aids in equalizing the temperature within each of the two tubes.

The above described methods are also operative for the preparation of a carrier gas from propane, butane, hexane, natural gasoline and other like hydrocarbon products, which do not contain major quantities of olefins and or aromatics and therefore can be directly treated catalytically With steam Without carbon deposition. For the treatment of such starting materials, the apparatus and methods of the present invention oier the advantage of higher permissible space velocities, i. e., greater yields per hour of carrier gas are obtained for each unit volume of catalyst. In other Words, a plant according to the present invention is characterized by high capacity. This is of great importance in connection with installations for periodic or seasonal operation to meet peak load demands Where the capital investment in apparatus is a major cost item.

A plant for carrying out the manufacture of substitute gas according to the preferred method of the present invention is shown diagrammatically and by Way of an illustrative example in Figure 2. This plant includes a furnace IIl of suitable fire resistant material enclosing a space divided into two compartments by a baiiie I2 depending irom the roof. The enclosed space is heated by burners It, for instance, two burners to the left of the baffle and one burner to the right. Combustion gases are discharged through a stack I5. An empty cracking tube I6 extends vertically through the furnace to the right of the baiie While a tube I8 containing catalyst 2li extends vertically through the furnace to the left of the bafe I2. The bottom ends of the tubes i6 and I8 are connected by conduit 22 which is preferably insulated or otherwise protected against heat loss, so that gases passing therethrough from tube I 6 into tube IB are maintained, preferably, at at least 1000 F. If desired or 7 necessary.. the conduit. 21: may be externally heated.

A mixtureof hydrocarbon vapor and Steam.. enters into the tube. I6k from a conduit 2 4 for initial crac-king and concurrent blue gas reaction (jas described. hereinabove). Hot air is added to. the reaction product issuing from tube I6 into conduit 22., for instance, from the tube 25. The mixture of carrier gas and steam issuing from the tube i6 passes through a conduit 26, a first heat exchanger 26, a conduit 30, a second heat exchanger 32, a conduit 3H, and a third heat exchanger 36 into conduit 38. The latter may discharge, if desired, into a cooler 60 and thegas may pass therefrom through a conduit 42, a condenser fit! and a conduit 46. into a water Washer 48.. The Water from the Washer is discharged through a. conduit 5.0 and the carrier gas through a conduit 52.

Butane or propane may be conducted Vfrom a suitable source (not shown) through a conduit 5.6, through the third heat exchanger 36, through a conduit 55, and through a fourth heat exchanger 56 into a branched conduit 58 for blending With the carrier gas in the conduits 38 o r 52. Air or iiue gas may be added to the resulting mixture through the conduit 59 to form the nished substitute gas.

A liquid hydrocarbon mixture from a suitable source (not shown) passes through a conduit 60, the second heat exchanger 32, a conduit 6|, a fth heat exchanger 62 and a conduit 64 into the conduit 2id. Superheated steam may be generated by passing water through a conduit 66, through the first heat exchanger 28, through a conduit 6l', through a sixth heat exchanger 68 and through a conduit T0, part of which extends Within the furnace i0, and thereafter conducted into the junction of the tWo conduits 24 and 64.

The heat exchangers 68, 62 and 56 are heated by combustion gases from the furnace l discharged through the stack I into the heat exchanger 68, therefrom through conduit 'I2 into the heat exchanger 62 and therefrom through conduit Ill into the heat exchanger 56 from which the combustion gases are vented through a duct '16. The heat exchangers 28, 32 and 36 are heated by the mixture of carrier gas and steam discharged from the catalyst tube I8 through conduit 26.

The hot air entering the conduit 22 vfrom conduit 25 is obtained by means of a compressor 18 forcing air through a conduit 80, part of which extends Within the furnace l0.

The operation of the above described plant involves the preferred method discussed in connection with the iiow sheet. Over and above the steps disclosed in connection with the fiovv sheet, the specific plant described hereinabove by Way of example utilizes the heat contents both of the combustion gases from the furnace and O f the product issuing from the second or catalyst tube to preheat the hydrocarbon material entering into the first reaction tube; to vaporize the propane or butane or other material forming the enriching gas; and to generate and superheat the steam passing through the reaction device. It should be understood that the above recovery of heat from thel combustion gases and from the mixed carrier gas or steam from the second or catalyst tube can be carried out concurrently and that, if desired, heat can be recovered from either source to the exclusion of the other.

Specific results obtained according to the preferred method are given hereinbelow. The starting material; used was a cracked; gasoline hanna the following characteristics. :y

A. P. I gravity F'. 58.9 Sp. Gr. 60/60" F 0.7432

Heating value:

B. t. u. per gallon 125,300 B.. t. u. per pound 20,240

A. S. T. M. disillation:

During the first 156 hours of the run the. conditions tabulated hereinbelovv were maintained. Thereafter conditions were changed andthe run was continued for another 49. hours. Throughout this time, all the steam was added ahead of the rst tube and all the airl after the first tube but ahead of the second tube. The conditions and results obtained are tabulated hereinbelow, with the first vertical column of figures showing the conditions and results for the rst 156hours and thesecond vertical column of figures showing the conditions and results for the last 49 hours:

156 hours 4Q hours Furnace temperature, F l, 850 l, 850 Hydrocarbon feed, gallons/hr 1.6 2.2 Steam, lbs/gall in feed .1 26 2 0 Air, cu. iwqailou feed 140 102 Cu. ft. carrier cas/gallon feed 547 489 Space-time-yield, cu. ft. carr catalyst-hr 1, 387 1 681i- Carrier gas analysis, nercent:

Carbon dioxide, GO2 S. 7 7-.'5 Illumlnantm. 0.4 '0.0 Oxygen, O2 0.2 0.1 Hydrogen, H2 50. 7 50.05 Carbon monoxide, C 1 8. 6 2l. 4 Parafns, CH2 N+z 2:8 4. 2 Nitrogen, N'z. 18. 6 .15'. 9 Specific Gravity 0. 56 0. 69 Heating value, B. t. u./c 263 l295 The mixed steam and gasoline vapors Were heated to from 800 to 1000 before being passed through the rst tube (an empty 2" alloy tube) at an average gas velocity of about 200 feet per second. The average time of contact of the mix! ture in the first tube amounted to slightly less than 0.1 second. The mixture issued from the rst tube at a temperature of from 1100 t o 1200 and passed at this temperature into'thje` second or catalyst tube which was filled 'with 3A inch cubes of refractory brick soaked Witha .con-s centrated 'nickel nitrate solution and'thereafter ignited, as described hereinabove. Thismaterial contained about 6.4% nickel'.

The gas fraction ofthe material issuing; rfrom 9 the first tube was characterized by the following analysis, specific gravity and heating value:

Per cent Carbon dioxide, CO2 9.6 Illuminants 16.1 Oxygen, O2 0.0 Hydrogen, H2 49.4 Carbon monoxide, CO 11.5 Methane, (3i-I4 7.5 Ethane, C21-Is 5.9 Nitrogen, N2 0.0

Total 100.0

Specific gravity 0,56I Heating value (B. t. u.) 62'? By way of comparison a run was made for '78 hours under the same conditions but with the second or catalyst tube empty. The conditions and results obtained are tabulated as follows:

Furnace temperature, F 1,850

Runs were also made with cracked gasoline omitting the iirst tube and passing a mixture of cracked gasoline vapors, steam and air through a tube lled with a catalyst containing 5% nickel.

The results of two runs are tabulated as follows:

Temperature, Mid Tube Wall, F 1,670 1, 660 Hydrocarbon Feed, gal/hr 0.15 0. 06 Steam, lb./hr 3.1 3. 3 Air. cu. it./hr 17.8 13.1 Hydrocarbon Feed, gal/cu. ft. cataly 1.6 0.7 Steam, lbs/cu. it. catalyst-hr 35 37 Air, cu. it./cu. ft. catalyst-hr 200 147 Carrier Gas:

cu. 57 29 cu. ft./ga1. feed 390 465 Space Time Yi d, cu. ft. catalyst-hr. 640 325 Carrier Gas Analysis, Percent:

Oz 4. 9 7. 6 llluminants 1. 5 2. 7

Oz 0.7 0.2 Hz- 39. 3 35. G GO 20. 0 16.8 Parafll 5.0 4. 3 N 2 28. 6 32.8 Specic gravity 0.63 0.68 Heating value, B. t. u./cu. ft 309 291 The first run had to be terminated after ve hours due to carbon deposition, and the second run after fourteen hours for the same reason.

It is therefore apparent that we have invented an improved process and apparatus for gasifying normally liquid hydrocarbons including, as essential features, a pre-heating and thermal selective cracking of a vaporized hydrocarbon mixture in an atmosphere of steam and a further catalytic cracking in the presence of steam and preferably also of air, a blue gas reaction taking place concurrently with both cracking steps. A great advantage of this process is the fact that the process can be carried out for long periods of time without need for catalyst regeneration for removal of carbon deposits and without formation of tars or oils in amounts sulcient to foul the cooling or condenser system. A carrier gas suitable for enrichment with propane or butane vapors or with conventional oil gas can be generated at low cost, since the normally liquid starting material does not require storage under pressure.

Many details for construction, composition and procedure may be varied within a wide range without departing from the principles of this invention and without sacricing the above indicated advantages. It is, therefore, not our purpose to limit the patent granted on this invention otherwise than necessitated by the scope of the appended claims.

We claim as our invention:

1. A method of preparing a gas 'interchangeable with coke oven gas, carburetted water gas or mixtures thereof, said method comprising providing a normally liquid hydrocarbon mixture containing a substantial amount of non-parafiinic ingredients and characterized by deposition of non-gaseous material on contact with a high activity cracking catalyst at cracking temperature in the presence of steam, vaporizing said mixture, adding to the resulting vapor steam in an amount ranging from 0.5 to 12 pounds for each pound of vapor, cracking the hydrocarbon Vapor at from 800 to 1700o E'. in the presence of said added steam but in the absence of a high activity cracking catalyst, separating a normally gaseous and a normally liquid fraction from the resulting product, contacting said normally liquid fraction with a high activity cracking catalyst at from 1000 to 2000o F., incorporating said norN mally gaseous fraction with the product from said catalytic step to enrich the latter, and adjusting the specific gravity of the enriched gas with a gas of high speciiic gravity.

2. A method of preparing a gas interchangeable with coke oven gas, carburetted water gas or mixtures thereof, said method comprising providing a normally liquid hydrocarbon mixture containing a substantial amount of non-paraf finie ingredients and characterized by deposition of non-gaseous material on contact with a heavy metal cracking catalyst at cracking temperature in the presence of steam, vaporizing said mixture, adding to the resulting vapor steam in an amount ranging from 0.5 to 12 pounds for each pound of Vapor, thermally cracking the hydrocarbon vapor at from 800 to 1700 F. in the presence of said added steam but in the absence of a cracking catalyst to form a product comprising a normally liquid fraction and a normally gaseous fraction containing major proportions of hydrogen, carbon oxides, illuminants, methane and ethane, adding to the resulting product air in an amount ranging up to cubic feet for each pound of said vapor, contacting the resulting air and steam-containing mixture with a heavy metal cracking catalyst at from .1.300u to 1850 F., thereafter removing steam from the resulting product, enriching the residual gas with a hydrocarbon-containing gas, and adjusting the specific gravity of the enriched gas with a gas having a high specific gravity.

3. A method of preparing a gas interchangeable with coke oven gas, carburetted water or mixtures thereof, said method comprising providing a normally liquid hydrocarbon mixture containing a substantial amount of non-parar` africana ni'c ingredients and characterized by deposition of non-'gaseous material on Contact with aheavy metal cracking catalyst at cracking temperature in the presence of steam, vaporizing said mixture, adding to the resulting vapor stearnin an amount ranging from `0.5 to 12 .pounds for each pound of vapor, thermally cracking the hydrocarbon vapor at from 800 to V1700"'11.v in the presence of said added steam, but in the absence of a cracking catalyst to form a product comprising a normally liquid fraction and a normally gaseous fraction, contacting the normally liquid `fraction with a heavy metal cracking catalyst at from 1000 to 2000 F., enriching the gas produced by such contacting with a hydrocarbon containing gas and adjusting the specific gravity of the enriched gas with a vgashaving a high specific gravity.

4. A method of preparing a gas interchangeable with coke oven gas, 'carburettedwater gas or mixtures thereof, said method comprising providing a normally liquid hydrocarbon `mixture containing asubstantial amount of; non-parafinic ingredients and'chara'cterized by deposition of non-gaseous material on contact with a heavy metal cracking catalyst at cracking temperature in the presence of steam, vaporizing said mixture, adding to the4 resulting vapor steam in an amount ranging from 0.5 to 12 pounds for each pound of vapor, thermally cracking the hydrocarbon vapor at from 800 to 1700o F. in the presence of said added steam but in the absence of a cracking catalyst to :form a product comprising a normallyliquid fraction and a normally gaseous fraction gmtaining major proportions of hydrogen, carbon oxides, illuminants, methane and ethane, contacting the resulting steam-containing product with a heavy metal crackin-'gi' catalyst at from 1300 to 1850'F. to convert all of said product to a gas, thereafter removing steam from the gaseous product of said contacting, enriching the residual gas with a hydrocarbon-containing gas, and adjusting the specific gravity of the enriched gas with a gas having a high specific gravity.

References Cited in the le 'of' this patent UNITED STATES PATENTS Number Name Date 520,401 Johnson et al. 1May122, 1894 1,454,609 Winter May 18, 1923 1,796,299 Nolan Mar. 17, 1931 1,843,063 Burke Jan. 26, 1932 1,846,235 Wade 23, 1932 1,874,801 Porter' .430, 1932 1,902,004 Whitlock Mar. 21, 1933 1,904,592 Young et al. Apr. 18, 1933 1,904,908 Voorhees Apr. 1 1933 1,918,254 Faber July 18, 1933 1,929,665 Wilcox Oct. v10, 1933 1,992,909 Davis Feb. 26,1935 2,056,911 Schiller et al Oct. 6, 1936 2,077,236 Harris Apr. 13, 1937 2,085,510 Rider June 29, 1937 2,53'7,*.08I Scharmann Jan. 9, 1951 2,541,569 Born Feb, 1-3, 1951 FOREIGN PATENTS Number Country Date 5,510 Australia Jan. 11, '1927 255,423 Great Britain Aug. 19, 1927 293,007 Great Britain Nov. 8, 1928 296,785. Great Britain De'cu4, 1929 147,100

Switzerland May 31, 1931 

1. A METHOD OF PREPARING A GAS INTERCHANGEABLE WITH COKE OVEN GAS, CARBURETTED WATER GAS OR MIXTURES THEREOF, SAID METHOD COMPRISING PROVIDING A NORMALLY LIQUID HYDROCARBON MIXTURE CONTAINING A SUBSTANTIAL AMOUNT OF NON-PARAFFINIC INGREDIENTS AND CHARACTERIZED BY DEPOSITION OF NON-GASEOUS MATERIAL ON CONTACT WITH A HIGH ACTIVITY CRACKING CATALYST AT CRACKING TEMPERATURE IN THE PRESENCE OF STEAM, VAPORIZING SAID MIXTURE, ADDING TO THE RESULTING VAPOR STEAM IN AN AMOUNT RANGING FROM 0.5 TO 12 POUNDS FOR EACH POUND OF VAPOR, CRACKING THE HYDROCARBON 